With high-speed regeneration of recent optical disk media such as CD-ROM, DVD, etc., regenerating data in synchronization with data PLL independent of a transfer rate, that is, so-called jitter-free regeneration, is indispensable for improving access speed in the high-speed CAV regeneration (with constant motor revolution) and the CLV regeneration (with constant regeneration speed).
In the jitter-free regeneration, the features in the settings of a filter and an equalizer, the responsiveness of an AGC circuit, the responsiveness of a binary circuit, etc. are variable depending on a transfer rate, and are deteriorated in jitter margin, thereby requiring an operation of varying the setting or responsiveness depending on the transfer rate.
To solve the above described problem, a whole disk is divided into a plurality of zones depending on a data address to vary the settings and the responsiveness for each zone in the conventional CAV regenerating technology, or a transfer rate is computed from the width of a special pattern of binary data to vary the above described settings and the responsiveness depending on the result in the conventional CLV regenerating technology.
With the above described conventional configuration, it is necessary to divide a disk into a number of zones to obtain the optimum settings, thereby largely increasing the number of processes and the management scale. Furthermore, additional circuits such as a circuit for detecting a transfer rate are required. In addition, processes cannot be performed on writable media such as DVD-RAM, etc., especially on an unwritten area.